The talented James Kelly sent over a story at Kotaku featuring this intriguing prop/marketing tool.
The postcard leads to the Kingsmouth website, which is itself a marketing effort for "The Secret World", an upcoming conspiracy/supernatural MMO from Funcom. Kingsmouth appears to be one of the central game locations, and given the name (Kingsmouth = Kingsport/Innsmouth) it's role as a classic Lovecraftian small town, complete with dark secrets, underground tunnels, and horrific historical events, should come as no surprise.
The game looks like it could be ten flavors of awesome if, and it's a big if, the dev team is committed to producing a massive amount of content. I like first person shooters as much as anyone, but I think the audience for an occult mystery MMO is looking for more than just the bang bang. They want interesting stories and, dare I say it, actual mysteries. Crafting either is something few online games have had any success at, relying instead on contrived storylines that consist of collecting plot tokens. I'm skeptical, but if they can pull it off I'll happily plunk down my $15 a month.